Flat or low-sloped roofs are often covered with polymeric membranes, which protect the roof from environmental impact such as snow and rain.
These polymeric membranes are typically manufactured and shipped in widths that are narrower than the roof surface to which they are installed. Accordingly, multiple membranes are often installed, and adjacent membranes are seamed together.
Pressure sensitive seam tapes are often employed for this purpose. Specifically, a pressure sensitive seam tape is applied to one surface of a membrane along a longitudinal edge and an adjacent membrane is mated along its longitudinal edge to the top surface of the pressure sensitive seam tape to thereby form a seam.
Technologically useful pressure-sensitive seam tapes employed in the industry include cured or partially cured rubber. For example, U.S. Pat. No. 4,855,172 teaches an adhesive tape comprising cured butyl rubber. The rubber can be cross-linked with a bromomethylated phenolic resin and zinc oxide. The composition is typically manufactured by extruding a layer of green or uncured rubber to a coated release paper, rolling the extrudate and release paper, and then subjecting it to curing conditions for a specified period of time (e.g., one day at 70° C.). Similarly, U.S. Pat. No. 5,242,727 teaches a pressure-sensitive adhesive tape composition including a blend of an ethylene-propylene-diene terpolymer, a halogenated butyl rubber, polyisobutylene, a phenolic resin, zinc oxide, and a sulfur-based cure system. After the composition is extruded onto a release liner, it is heated to a temperature of about 100° C. for a period of two-six hours to achieve the desired cross-linking of the rubber.
While these pressure-sensitive adhesive tapes have proven to be technologically useful, they suffer from several drawbacks. First, they require significant cure time, which reduces manufacturing efficiencies and increases costs. Also, due to the level of curing, the compositions behave as thermoset materials and are therefore not reprocessable.
There is therefore a desire for pressure-sensitive adhesive tape compositions that are more easily manufactured, are reprocessable, and demonstrate the performance characteristics that have come to be expected from cured butyl rubber systems.